DROP COLUMNS¶
Function¶
This command is used to delete one or more columns from a table.
Syntax¶
ALTER TABLE [db_name.]table_name DROP COLUMNS (col_name, ...);
Parameter Description¶
Parameter | Description |
|---|---|
db_name | Database name. If this parameter is not specified, the current database is selected. |
table_name | Table name. |
col_name | Name of a column in a table. Multiple columns are supported. It consists of letters, digits, and underscores (_). |
Precautions¶
After a column is deleted, at least one key column must exist in the schema. Otherwise, an error message is displayed, and the column fails to be deleted.
Examples¶
Assume that the table contains four columns named a1, b1, c1, and d1.
Delete a column:
ALTER TABLE carbon DROP COLUMNS (b1);
ALTER TABLE test_db.carbon DROP COLUMNS (b1);
Delete multiple columns:
ALTER TABLE carbon DROP COLUMNS (b1,c1);
ALTER TABLE test_db.carbon DROP COLUMNS (b1,c1);
System Response¶
If you run the DESCRIBE command, the deleted columns will not be displayed.